Activity and particle size

Fluidized-bed reaction systems are not normally shut down for changing catalyst. Fresh catalyst is periodically added to manage catalyst activity and particle size distribution. The ALMA process includes faciUties for adding back both catalyst fines and fresh catalyst to the reactor. 

The time required for the hydrogenation will depend on several factors, such as the speed of shaking, activity and particle size of the catalyst. In the experiments run on ethyl p-nitro-phenylacetate the submitters have found that the time required varied from about 2 to 4 hours. 

Roller PS. Chemical activity and particle size. II. The rate of solution at slow stirring of anhydrite and gypsum. J Phys Chem 1932 36 1202-1231. 

Fig. 16) between halogeno-aryl and phenyl boronic acid with a strong relation between activity and particle size. Thus, the higher catalytic activity is obtained for catalyst with 2.5-3.5-nm particles. The increase of size of nanoparticles dramatically decreases the catalytic activity. 

In these experiments the correlation between catalytic activity and particle size was investigated using ethane-l,2-diol oxidation as a model reaction. In the presence... 

The rate at which milling products deteriorate under given conditions of storage is determined by level of lipase activity and particle size distribution 01 bran. In practical terms, storage of wholemeal at very low moisture and temperature is not feasible for several reasons. However, bran and germ may be stabilised by heat-moisture treatment and this is practised commercially. The relatively high heat stability of the lipase, precludes heat-treatment of wholemeal flour, because the essential functionality of wheat proteins is destroyed by less severe conditions than those required to inactivate the lipase. 

Specifications and Packaging. Aluminum chloride s catalytic activity depends on its purity and particle size. Moisture contamination is an important concern and exposure to humid air must be prevented to preserve product integrity. Moisture contamination can be deterrnined by a sample s nonvolatile material content. After subliming, the material remaining is principally nonvolatile aluminum oxide. Water contamination leads to a higher content of nonvolatile material. 

Rouse, A.H. 1951. Effect of insoluble solids and particle size of pulp on the pectinesterase activity in orange juice. R. State Hort. Soc. Proc. 64 162-166. 

Specific Activity (SA) and Mass Activity (MA) of Pt Electrocatalysts Supported on Different Carbon Powders Characterized by Specific Surface Area (S) and Particle Size (d)... 

CO electro-oxidation exhibits a strong particle size dependence on both carbon-and titania-supported Au catalysts a strong deactivation of the reaction is observed for particle sizes below about 3 nm. In the case of the titania supports, however, a distinct activation of the reaction is also evident. This manifests itself in a strong decrease in the overpotential for the reaction, and an increase in activity as the particle size decreases in the range 8-3 nm. The result is a maximum in the catalytic activity with particle size. 

The formulation of this type of product usually employs a small number of ingredients and sometimes only the active ingredient. Particle size and particle size distribution, rugosity, and particle charge should be considered for all ingredients, and the specific grade of excipients should be stated. The excipients should be sourced from a single supplier (with data to demonstrate the suitability of different batches of material), but if multiple sources are used, additional data will be required to establish the suitability of different batches from each supplier. 

The oxidative dehydrogenation of ethanolamine to sodium glycinate in 6.2 M NaOH was investigated using unpromoted and chromia promoted skeletal copper catalysts at 433 K and 0.9 MPa. The reaction was first order in ethanolamine concentration and was independent of caustic concentration, stirrer speed and particle size. Unpromoted skeletal copper lost surface area and activity with repeated cycles but a small amount of chromia (ca. 0.4 wt%) resulted in enhanced activity and stability. 

Stemmer M, Gerzabek MH, Kandeler E (1999) Invertase and xylanase activity of bulk soil and particle-size fractions during maize straw decomposition. Soil Biol Biochem 31 9-18... 

Figure 1.6 Representative TEM image (a) and particle size distribution (b) obtained for a Au/Ti02 catalyst prepared by grafting of a [Au6(PPh3)6](BF4)2 complex onto Ti02 particles followed by appropriate reduction and oxidation treatments [42], The gold particles exhibit approximately spherical shapes and an average particle size of 4.7 nm.The measured Au particle sizes could be well correlated with the activity of the catalyst for carbon monoxide oxidation and acetylene hydrogenation. (Reproduced with permission from Springer.)...

Lyon DY, Adams LK, Falkner JC, Alvarez PJJ (2006) Antibacterial activity of fullerene water suspensions Effects of preparation method and particle size. Environ. Sci. Technol. 40 4360 1366. 

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